1. Field of the Invention
The present invention relates to a toner for developing static charge images in an electrophotographic method, an electrostatic-printing recording method, and the like.
2. Description of Related Arts
In general, a toner having a negative charge property for developing static charge images, used in an electrophotographic method, is necessary for good fluidity. Therefore, on its surface, one or more agents for the fluidization is adhered. Further, the toner is used together with an iron powder or a ferrite carrier for developing static charge images so as to have optimal charge which is necessary to develop the images.
It has been known that powders of silica, titanium oxide, etc. are used as agents for the fluidization of the toner. When silica is used, the toner has a good fluidity. However, in this case, a decline of the image concentrations often occurs extended usage due to increased charge quantity. Further, the dependency of the humidity becomes stronger. Accordingly, in the condition of low humidity, a decline of the image concentrations particularly occurs due to marked increase of the charge quantity.
Alternatively, when titanium oxide is used, it can be suppressed to increase the charge quantity in the condition of low humidity, but the decrease in charge quantity, in the condition of high humidity, causes various problems, for example an increase in fog density and splashing of the toner.
In a color toner having a positive charged property for developing static charge images, a colloidal silica is generally used as the agent for the fluidization.
However, colloidal silica has essentially a strong negative charge property. Accordingly, during mixing with the carrier in the developing machine, the original charge quantity of the toner decreases, so that a toner using colloidal silica encounters various problems such as increase in fog density, splashing of the toner, and shortening of the developer's life due to lie the fluidizing agent in the developer.
In particular, the charging property of the color toner which includes a quaternary ammonium salt or a polyamine resin, is easily affected by the negative charge property of colloidal silica, and thus fogging and splashing of the toner during the development occurs frequently.
Further, when the color toner, on the surface of which the colloidal silica is adhered, is developed in the condition of high temperature and high humidity, the charge quantity of the toner decreases due to the moisture adsorption of the colloidal silica, causing various problems such as an increase of fog density. Additionally, in the condition of low temperature and low humidity, other various problems occur such as the decrease of the image concentrations due to increase of the charge quantity.